Fill in missing GL methods for TextureTest Bug: angleproject:4732 Change-Id: Ic475e29b6ca641029243712115d6a578a48c85f0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2241624 Commit-Queue: Manh Nguyen <nguyenmh@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com>